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Pressure sensor presentation slides.pptx

Introduction

Pressure sensor's function is based on physical phenomenon. It can be used at least two different situation:
water, air or between two points of measurement.

 

Table of Contents

Table of Contents
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Types of pressures and basic physics of pressure sensing

...

where P is the pressure (Pa), F is the force (N) and A is the area (m2). [1]

Force unit can be determined by F= m*a, (mass*acceleration).

Volume pressure, known as the density can be used when determining the volume of the container.

p (rho) = m (mass) / V (volume). [2.]



Archimedes's principle states can be determined by for example a person goes bath and the waterspills over bathtub. The amount of spilled
water has the same volume than a person.

Physical formula is: P= p*h*g

P = p (rho) * h (height in metres) *g (gravitation force (9,81 m/s^2))

Pascal's law states that an increase in pressure at any point in a liquid causes a corresponding increase at every other point in the
liquid. [32.]

For example if pressing a cylinder on the other side and because of the water is solid, second cylinder will be pulled out upward.

This method is a common in for example car brakes.

...

We chose as our Piezoelectric sensor a PiezoStar® Pressure Sensor Type 6125C. [(6])

Transfer function

Transfer function for piezoelectric transducer can be calculated as:

...

The system has some output noise which is approximately some hundreds of nV/sqrt(Hz). Noises are coming from voltage and current. [58; 69.] 

Piezoelectric sensors are usually very stable so they don't need calibration after purchasing but in extreme conditions characteristics may change over time. In this case the sensors are usually sen to the manufacturer. [10; 11]

Materials and manufacturing technologies

Piezoelectric sensors can be made from many different materials with complicated manufacturing processes.

The PiezoStar® Pressure Sensor Type 6125C’s structure is made of crystalline, so it does not contain silicon. In piezoelectric sensors there are usually used either Nickel (Ni) or Copper (Cu) or both. Because both of the metals are chemical elements they are nonferrous. [6.]

For piezoelectric materials are usually used ceramics, but also crystal can appear as one. The materials are also very sensitive to temperature changes. The mostly used substances are Zinc oxide, Aluminum nitride and PZT. The manufacturing process is complex and long-lasting. In PiezoStar sensors there is mainly used Kistlers own PiezoStar material. More information is available in piezoelectric sensing article about this subject. [14.]

The materials which used while manufacturing PiezoStar product are new crystals, similar as gallium orthophosphate (GaPO4) or langasite (La3Ga5SiO14). it is required to use these materials because of high working temperature (450 °C, even 700 °C). [15.]

Plastic is not used as a material in this kind of sensors because it wouldn’t cope with the massive pressure. Metal is harder and can take the pressure so it is a good material to use in this case. Ceramics and crystal are easier to get piezoelectric that’s why they are in common use.

Kistler PiezoStar® Pressure Sensor has about 200 manufacturing steps before it will reliable sensor and ready to use. First phase of manufacturing process is X-raying and it is used to determine factor in the properties of the sensor element.

All components are checked and measured extremely precise: after milling it is cutted, lapped and coated. Lastly it is re-coated. Quartz and crystal components can be cutted and measured precisely. Then it is easy to design how small the sensor will be. The sensor must be well designed to use hard circumstances: high-speed phenomena and high temperature [16.]

Sources

  1. Pressure definition:, http://www.school-for-champions.com/science/pressure.htm#.U1ilsRDFJ8E
  2. Archimedes' Law: , http://www.auburn.edu/~nzk0001/pub/phys1600/10_archimedes.pdf
  3. Determining the density: , http://physics.about.com/od/fluidmechanics/f/density.htm
  4. Preeti Jain, Pressure Sensors,  http://www.engineersgarage.com/articles/pressure-sensors-types-working
  5. Robert E. Bicking, Fundamentals of Pressure Sensor Technology  1998,  http://www.sensorsmag.com/sensors/pressure/fundamentals-pressure-sensor-technology-846
  6. PiezoStar® Pressure Sensor Datasheet by Kistler
  7. Piezoelectric Transducers and Applications, editor: Antonio Arnau Vives
  8. Eduardo Bartolome, Signal conditioning for piezoelectric sensors,  http://www.ti.com/lit/an/slyt369/slyt369.pdf
  9. CONVENTIONAL CHARGE OUTPUT SENSORS,  http://www.pcb.com/TechSupport/tech_signal
  11. Accuracy and Calibration Calibration, http://www.mmf.de/accuracy_and_calibration.htm

...

  1. Composite materials, https://www.americanpiezo.com/products-services/composite-materials.html
  2. New Piezoelectric Materials Improve Sensor Performance, https://www.sem.org/PDF/kistler_PiezoStar.pdf
  4. Manufacturing and materials of piezoelectric sensor http://www.ama-science.org/proceedings/getFile/AQx2
  5. Manufacturing steps http://www.kistler.com/medias/sys_master/8812119097374/100-460e-12.10.pdf